Ok, I could accept that - except that gio uses *message* and *post*Looking at the Settings page with fresh eyes I see what you mean. (And I would prefer to settle on /message/, see below).
E.g. the Message Policies section:
|_| Allow Non Subscribers to Post
Posts by non-subscribers will be moderated, instead of rejected.
The first usage is simply an implied object ("... to Post Messages"), but the second is a nominalization. It could be corrected as "Messages from non-subscribers..." (or "Posting by non-subscribers...").
Arguably the correction to "Messages from" would be an improvement.
I note that sometimes GMF gets questions that imply a belief that the Moderated setting also causes other content (Files, Photos) from members to also be held pending. Specifically:
All posts require approval before being sent to the group.
and also (in a member's membership page):
o Use Group Moderation Setting
In both those contexts "post" may be interpreted more broadly than just messages, and absent any moderation controls specific to Files or Photos some people use (or hope for or wish for) the broader interpretation.